GEOLOGICAL SURVEY OF THE TERRITORIES. 



395 



middle does not relate to either of those anterior or posterior to it. 

 There are, therefore, at least four lost from that region also. 



There is a considerable interruption immediately anterior to the last 

 dorsal vertebra. Three large vertebrae, with long diapophyses belong- 

 ing here, were imbedded in the hard matrix which protected the pelvic 

 arch. These are far from relating immediately to the vertebrae preserved 

 before and behind them. I estimate the number missing as follows: 

 Seven of the fourteen dorsals preserved have more or less elongate dia- 

 pophyses. In the Plesiosauri, vertebrae of this character are much more 

 numerous; in P. homalospondylus Owen gives seventeen. If we add 

 ten to the series in the present species it will give the abdominal space 

 between the adjacent margins of the o. o. pubis and coracoidea an ex- 

 tent equal to the length of the plevic arch. This is relatively shorter 

 than in the Plesiosauri. Dr. Turner found that a space of "three or 

 four" feet intervened between the two portions of the skeleton, which 

 was otherwise continuous. I think ten an average number to represent 

 safely the missing dorsals. 



From the cervical proximal regions probably three vertebrae are miss- 

 ing from two interruptions. The remainder of the servical series ex- 

 hibits three interruptions. Most of the proximals have been broken 

 medially, leaving the articulations solid, an advantage in determining 

 their continuity. Three vertebrae and one-half are thus found to be 

 missing in this region. 



The whole number of vertebrae preserved and lost, with the relative 

 lengths of each, may be stated as follows: 



This gives the total length to the animal of forty-three feet two 

 inches, which, increased by the amount taken up by intervertebral 

 cartilages, will give roundly about forty-five feet. Of this, twenty-two 

 feet must be reckoned to the neck. 



The cervical vertebrae are assumed to commence where the rib pits 

 cease, and the continuous lateral processes commence. This point is 

 ascertained with difficulty on the specimen. It is, however, perhaps 

 the same point where the longitudinal lateral ridge leaves the upper 

 margin of the rib pit; and it was to the series of vertebrae which pass 

 this point, the scapular bones, the clavicle and coracoid, were found 

 attached. On the anterior dorsals the inferior margin of the rib pit is 

 most prominent, and is finally produced in a fiat thin process which is 

 directed obliquely downwards. Both these and the posterior ribs are 

 crushed on the centra and project obliquely below them ; their mode 4 

 of attachment is thus rendered rather obscure. A similar structure ex- 

 ists in the posterior cervicals of Gimollasaurus, while on the anterior 

 dorsals, or where the rib-origins are on the lower plane, short, thick dia- 



